Electron-spin-resonance studies of AlGaN/GaN MIS-HEMT structures with Al2O3 fabricated by atomic layer deposition

We performed electron-spin-resonance (ESR) investigations of defects related to dangling bonds (DBs) around the insulator/semiconductor interface in Al₂O₃/AlGaN/GaN MIS-HEMT structures on Si. The Al₂O₃ layer was fabricated by atomic layer deposition, and we studied the effects of the Al₂O₃ layer thickness and the post-deposition annealing (PDA) temperature on the number of DBs (N_db). The N_db of the AlGaN/GaN HEMT structure was reduced by deposition of the 10-nm-thick Al₂O₃ layer. The N_db value at the 5-nm-thick Al₂O₃/AlGaN interface decreased to a minimum value with PDA at 500 °C. We show that defects related to DBs around ALD-Al₂O₃/AlGaN interfaces can be reduced by optimizing the ALD-Al₂O₃ thickness and PDA temperature.